Make FillBlock consume txn_available to avoid shared_ptr copies

Author: sipa

src/blockencodings.cpp

@@ -142,8 +142,9 @@ bool PartiallyDownloadedBlock::IsTxAvailable(size_t index) const {
     return txn_available[index] ? true : false;
 }
 
-ReadStatus PartiallyDownloadedBlock::FillBlock(CBlock& block, const std::vector<CTransactionRef>& vtx_missing) const {
+ReadStatus PartiallyDownloadedBlock::FillBlock(CBlock& block, const std::vector<CTransactionRef>& vtx_missing) {
     assert(!header.IsNull());
+    uint256 hash = header.GetHash();
     block = header;
     block.vtx.resize(txn_available.size());
 
@@ -154,8 +155,13 @@ ReadStatus PartiallyDownloadedBlock::FillBlock(CBlock& block, const std::vector<
                 return READ_STATUS_INVALID;
             block.vtx[i] = vtx_missing[tx_missing_offset++];
         } else
-            block.vtx[i] = txn_available[i];
+            block.vtx[i] = std::move(txn_available[i]);
     }
+
+    // Make sure we can't call FillBlock again.
+    header.SetNull();
+    txn_available.clear();
+
     if (vtx_missing.size() != tx_missing_offset)
         return READ_STATUS_INVALID;
 
@@ -170,10 +176,10 @@ ReadStatus PartiallyDownloadedBlock::FillBlock(CBlock& block, const std::vector<
         return READ_STATUS_CHECKBLOCK_FAILED;
     }
 
-    LogPrint("cmpctblock", "Successfully reconstructed block %s with %lu txn prefilled, %lu txn from mempool and %lu txn requested\n", header.GetHash().ToString(), prefilled_count, mempool_count, vtx_missing.size());
+    LogPrint("cmpctblock", "Successfully reconstructed block %s with %lu txn prefilled, %lu txn from mempool and %lu txn requested\n", hash.ToString(), prefilled_count, mempool_count, vtx_missing.size());
     if (vtx_missing.size() < 5) {
         for (const auto& tx : vtx_missing)
-            LogPrint("cmpctblock", "Reconstructed block %s required tx %s\n", header.GetHash().ToString(), tx->GetHash().ToString());
+            LogPrint("cmpctblock", "Reconstructed block %s required tx %s\n", hash.ToString(), tx->GetHash().ToString());
     }
 
     return READ_STATUS_OK;

src/blockencodings.h

@@ -202,7 +202,7 @@ class PartiallyDownloadedBlock {
 
     ReadStatus InitData(const CBlockHeaderAndShortTxIDs& cmpctblock);
     bool IsTxAvailable(size_t index) const;
-    ReadStatus FillBlock(CBlock& block, const std::vector<CTransactionRef>& vtx_missing) const;
+    ReadStatus FillBlock(CBlock& block, const std::vector<CTransactionRef>& vtx_missing);
 };
 
 #endif

src/test/blockencodings_tests.cpp

@@ -85,17 +85,23 @@ BOOST_AUTO_TEST_CASE(SimpleRoundTripTest)
         BOOST_CHECK_EQUAL(pool.size(), poolSize - 1);
 
         CBlock block2;
-        std::vector<CTransactionRef> vtx_missing;
-        BOOST_CHECK(partialBlock.FillBlock(block2, vtx_missing) == READ_STATUS_INVALID); // No transactions
+        {
+            PartiallyDownloadedBlock tmp = partialBlock;
+            BOOST_CHECK(partialBlock.FillBlock(block2, {}) == READ_STATUS_INVALID); // No transactions
+            partialBlock = tmp;
+        }
 
-        vtx_missing.push_back(block.vtx[2]); // Wrong transaction
-        partialBlock.FillBlock(block2, vtx_missing); // Current implementation doesn't check txn here, but don't require that
+        // Wrong transaction
+        {
+            PartiallyDownloadedBlock tmp = partialBlock;
+            partialBlock.FillBlock(block2, {block.vtx[2]}); // Current implementation doesn't check txn here, but don't require that
+            partialBlock = tmp;
+        }
         bool mutated;
         BOOST_CHECK(block.hashMerkleRoot != BlockMerkleRoot(block2, &mutated));
 
-        vtx_missing[0] = block.vtx[1];
         CBlock block3;
-        BOOST_CHECK(partialBlock.FillBlock(block3, vtx_missing) == READ_STATUS_OK);
+        BOOST_CHECK(partialBlock.FillBlock(block3, {block.vtx[1]}) == READ_STATUS_OK);
         BOOST_CHECK_EQUAL(block.GetHash().ToString(), block3.GetHash().ToString());
         BOOST_CHECK_EQUAL(block.hashMerkleRoot.ToString(), BlockMerkleRoot(block3, &mutated).ToString());
         BOOST_CHECK(!mutated);
@@ -181,17 +187,24 @@ BOOST_AUTO_TEST_CASE(NonCoinbasePreforwardRTTest)
         BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[2]->GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 1);
 
         CBlock block2;
-        std::vector<CTransactionRef> vtx_missing;
-        BOOST_CHECK(partialBlock.FillBlock(block2, vtx_missing) == READ_STATUS_INVALID); // No transactions
+        {
+            PartiallyDownloadedBlock tmp = partialBlock;
+            BOOST_CHECK(partialBlock.FillBlock(block2, {}) == READ_STATUS_INVALID); // No transactions
+            partialBlock = tmp;
+        }
 
-        vtx_missing.push_back(block.vtx[1]); // Wrong transaction
-        partialBlock.FillBlock(block2, vtx_missing); // Current implementation doesn't check txn here, but don't require that
+        // Wrong transaction
+        {
+            PartiallyDownloadedBlock tmp = partialBlock;
+            partialBlock.FillBlock(block2, {block.vtx[1]}); // Current implementation doesn't check txn here, but don't require that
+            partialBlock = tmp;
+        }
         bool mutated;
         BOOST_CHECK(block.hashMerkleRoot != BlockMerkleRoot(block2, &mutated));
 
-        vtx_missing[0] = block.vtx[0];
         CBlock block3;
-        BOOST_CHECK(partialBlock.FillBlock(block3, vtx_missing) == READ_STATUS_OK);
+        PartiallyDownloadedBlock partialBlockCopy = partialBlock;
+        BOOST_CHECK(partialBlock.FillBlock(block3, {block.vtx[0]}) == READ_STATUS_OK);
         BOOST_CHECK_EQUAL(block.GetHash().ToString(), block3.GetHash().ToString());
         BOOST_CHECK_EQUAL(block.hashMerkleRoot.ToString(), BlockMerkleRoot(block3, &mutated).ToString());
         BOOST_CHECK(!mutated);
@@ -200,7 +213,7 @@ BOOST_AUTO_TEST_CASE(NonCoinbasePreforwardRTTest)
         block.vtx.clear();
         block2.vtx.clear();
         block3.vtx.clear();
-        BOOST_CHECK_EQUAL(pool.mapTx.find(txhash)->GetSharedTx().use_count(), SHARED_TX_OFFSET + 1);
+        BOOST_CHECK_EQUAL(pool.mapTx.find(txhash)->GetSharedTx().use_count(), SHARED_TX_OFFSET + 1); // + 1 because of partialBlockCopy.
     }
     BOOST_CHECK_EQUAL(pool.mapTx.find(txhash)->GetSharedTx().use_count(), SHARED_TX_OFFSET + 0);
 }
@@ -240,8 +253,8 @@ BOOST_AUTO_TEST_CASE(SufficientPreforwardRTTest)
         BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[1]->GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 1);
 
         CBlock block2;
-        std::vector<CTransactionRef> vtx_missing;
-        BOOST_CHECK(partialBlock.FillBlock(block2, vtx_missing) == READ_STATUS_OK);
+        PartiallyDownloadedBlock partialBlockCopy = partialBlock;
+        BOOST_CHECK(partialBlock.FillBlock(block2, {}) == READ_STATUS_OK);
         BOOST_CHECK_EQUAL(block.GetHash().ToString(), block2.GetHash().ToString());
         bool mutated;
         BOOST_CHECK_EQUAL(block.hashMerkleRoot.ToString(), BlockMerkleRoot(block2, &mutated).ToString());
@@ -250,7 +263,7 @@ BOOST_AUTO_TEST_CASE(SufficientPreforwardRTTest)
         txhash = block.vtx[1]->GetHash();
         block.vtx.clear();
         block2.vtx.clear();
-        BOOST_CHECK_EQUAL(pool.mapTx.find(txhash)->GetSharedTx().use_count(), SHARED_TX_OFFSET + 1);
+        BOOST_CHECK_EQUAL(pool.mapTx.find(txhash)->GetSharedTx().use_count(), SHARED_TX_OFFSET + 1); // + 1 because of partialBlockCopy.
     }
     BOOST_CHECK_EQUAL(pool.mapTx.find(txhash)->GetSharedTx().use_count(), SHARED_TX_OFFSET + 0);
 }